Search results for "Alkaloid"

New Studies and a Reinvestigation on [4+2] Cycloadditions of (−)-Thebaine: Asymmetrical Diels-Alder Reactions with a Conformationally Fixed Chiral Di…

1993

Some novel Diels-Alder reactions of the opium alkaloid (−)-thebaine (1) as an electron-rich diene and a reinvestigation of its reactions with cyclic and acyclic dienophiles are described. The π-facial selectivity has been studied on the basis of structural analyses of the cycloadducts. Some related results on [4 + 2] cycloaddition reactions of 1-methoxy-1,3-cyclohexadiene (11) are also reported.

Enzymatic biosynthesis of raumacline

1995

Abstract The indole alkaloid, raumacline, is biosynthesized from ajmaline, when the latter was fed to cell suspensions of Rauwolfia serpentina . Formation in catalysed by two enzymes, a cell wall-bound peroxidase followed by a NADPH 2 -dependent reductase. The first enzyme cleaves ajmaline oxidatively leading to a C-21 epimeric mixture of 21-hydroxyraumacline, a novel alkaloid, which, in turn, is reduced under formation of raumacline. The peroxidase reaction is not specific for Rauwolfia cells whereas the reductase is present exclusively in Rauwolfia cell suspensions. The reductase has been purified to homogeneity. The enzyme is highly substrate specific, only accepting 21-hydroxyraumacline…

Biosynthesis of Monoterpenoid Indole Alkaloid Ajmaline Catalyzed by Novel Reductases1

2006

Chapter 2 Biosynthesis in Rauwolfia serpentina Modern Aspects of an Old Medicinal Plant

1995

Publisher Summary This chapter discusses a research on Rauwolfia , which was achieved after the generation of a cell suspension with extraordinary growth characteristics and physiological behavior. The investigations demonstrated that a range of techniques is now available for the clarification of complete metabolic pathways, provided that the appropriate efficient biological system is available. The isolation and identification of each single enzyme have almost become routine, even if an extremely sensitive protein analytic technique is necessary when several kilograms of fresh plant cells are reduced to a few micrograms of homogenous protein. The successful identification of a total of 20…

ChemInform Abstract: Alkaloid Determination in Crude Extracts from Cortex Quebracho and Opium Applying Capillary Electrophoresis and Capillary Electr…

2010

The applicability of capillary electrophoresis with UV and electrospray ionisation (ESI)-mass spectrometric detection to the determination of alkaloids in crude extracts of Cortex Quebracho and opium has been investigated. The use of a buffer electrolyte consisting of aqueous ammonium acetate (pH 3.1) and acetonitrile resulted in a high performance of peak resolution. Most of the alkaloids have been identified according to the signal of the protonated molecular ion in the ESI mass spectrum

1,2-Asymmetric Induction in Diastereo­selective Zwitterionic Aza-Claisen Rearrangements: Key Steps in Optically Active Alkaloid Synthesis

2013

The zwitterionic aza-Claisen rearrangement of optically active N-allylpyrrolidines and α-phenoxyacetyl fluorides proceeds with complete simple diastereoselectivity (internal asymmetric induction) and complete 1,2-asymmetric induction to generate a new C–C bond adjacent to a chiral C-N-Boc functionality. The resulting γ,δ-unsaturated amides were cyclised to give the corresponding pyrrolizidinones, which enabled the determination of the relative configuration of the stereotriads. Vinyl group degradation and a final lactam reduction gave an optically active analogue of (+)-petasinine (a pyrrolizidine alkaloid). Furthermore, the stereotriad-containing amides should be useful key intermediates f…

ChemInform Abstract: New Studies and a Reinvestigation on (4 + 2) Cycloadditions of (-)- Thebaine: Asymmetrical Diels-Alder Reactions with a Conforma…

2010

Some novel Diels-Alder reactions of the opium alkaloid (−)-thebaine (1) as an electron-rich diene and a reinvestigation of its reactions with cyclic and acyclic dienophiles are described. The π-facial selectivity has been studied on the basis of structural analyses of the cycloadducts. Some related results on [4 + 2] cycloaddition reactions of 1-methoxy-1,3-cyclohexadiene (11) are also reported.

The hedgehog receptor patched is involved in cholesterol transport.

2011

International audience; BACKGROUND: Sonic hedgehog (Shh) signaling plays a crucial role in growth and patterning during embryonic development, and also in stem cell maintenance and tissue regeneration in adults. Aberrant Shh pathway activation is involved in the development of many tumors, and one of the most affected Shh signaling steps found in these tumors is the regulation of the signaling receptor Smoothened by the Shh receptor Patched. In the present work, we investigated Patched activity and the mechanism by which Patched inhibits Smoothened. METHODOLOGY/PRINCIPAL FINDINGS: Using the well-known Shh-responding cell line of mouse fibroblasts NIH 3T3, we first observed that enhancement …

Green coffee, bioactive compounds’ analysis of experimental cultivation in Sicily: a new frontier in the Sicilian food sector

2023

Recently, climate change represents a new possibility for tropical cultivars fruit in Mediterranean areas. The focus of this work is the evaluation of the real possibility of coffee cultivation in Sicily, like coffee plants grown in tropical and subtropical regions. The objective was to evaluate plant adaptation to our climate and to study the chemical qualities of green coffee pulps and seeds: total phenolic content, antiradical capacity, fatty acids, amino acids, alkaloids, vitamins, proximate composition, polyphenolic profile and other bioactive compounds of cosmetic, pharmaceutical and agrary interest. Temperature, light and vegetative growth of Coffea arabica L. cv. “Caturra” plants we…

Selective chiral inhibition of Ca2+ entry promoted by bisbenzyltetrahydroisoquinolines in rat uterus.

1992

Abstract The effects of diltiazem and six bisbenzyltetrahydroisoquinoline alkaloids (antioquine, 7-O-methylantioquine, dimethylantioquine, monterine, granjine and cordobimine) were studied in rat isolated uterus in order to clarify the mechanisms of their relaxant actions. All the compounds tested completely relaxed KCl-induced contractions and totally or partially inhibited oxytocin-induced rhythmic contractions. Only alkaloids with absolute configurations (1R,1′S or 1R,1′R) acted intracellularly, promoting relaxation of contractile responses induced by oxytocin in a Ca2+-free medium, as does papaverine. Alkaloids of the antioquine series (1S,1′R) selectively inhibited Ca2+ entry. The grea…